Hi,

 

I'm flyig the Q400 (as we speak) and I encounter a strange issue.

At cruise level the (auto) TRQ setting is 68%. This appeared a bit too high because I'm at lower cruise level (FL240),

so the speed reached the overspeed zone.

Instead of pulling back the throttle lever a bit, I first wanted to try to use 850 RPM.

When I pulled the Cond Levers one noth back to 850, the following happend:

 

 

The 2nd prop suddenly has 1060 RPM and there is no way to change this anymore.

(moved the CL's several times)

Also I have now different TRQ modes (MCP and MCR)

 

Anyone a clue what is going on?

It happens in the real aircraft too if you accidentally move the CL lever below the 850 detent, the only way to clear it is to shut down that engine and restart it. This has been covered a couple of times here and at the Maajestic forum if you want further confirmation.

Ahhhh, thanks a lot for explaining.

Next time better do a search before posting

Egbert Drenth, on 19 May 2013 - 09:27 AM, said:

Hi,

 

I'm flyig the Q400 (as we speak) and I encounter a strange issue.

At cruise level the (auto) TRQ setting is 68%. This appeared a bit too high because I'm at lower cruise level (FL240),

so the speed reached the overspeed zone.

Instead of pulling back the throttle lever a bit, I first wanted to try to use 850 RPM.

When I pulled the Cond Levers one noth back to 850, the following happend:

just as an aside... typically you should be using 850rpm during cruise anyway. the reason you are getting overspeed is because you are cruising in climb power (as shown on your left engine). the MCR rating takes your altitude into account i believe.. if you want to cruise slower then reduce throttle slightly.

 

cheers

-andy crosby

Like Andydigital said, this is a feature present on the actual aircraft. Its the AUPC (automatic underspeed protection circuit) which prevents prop underspeed while inflight with autofeather off and CL above start/feather. If the system detects RPM below 816, while torque above 50% for 1 second, the Props will be sent into an overspeed condition with the PEC caution lights coming on. If your setting cruise power to MIN but you accidentally skip the detent and go to START/FEATHER and then back to MIN you will create all the conditions for this to happen. It has happened to a few RW airlines and they were only able to clear the overspeed after they landed.